The present invention relates to a wiring device commonly known as a cap or a connector of the character described in the above applications. A distinction in the article of the present invention from that of those mentioned above is that the present invention relates to a structure having additional electrical capacity in the form of five wires for carrying electric current. The above described devices relate primalily to the structure of the insulating housing of the device rather than to its electrical utility of one sort or another. It is well known that electrical caps and connectors are the common designation of wiring devices which are employed to provide terminals to cables which carry power from power sources to apparatus in which the power may be utilized. The power source may be a wall receptacle and a cap is normally employed to connect into the wall receptacle to power the cable extending from the cap. The apparatus in which power may be utilized may be, for example, a machine and the machine may be permanently connected to the power cable by some internal mechanism. Alternatively, there may be a connector at the end of the cable and the connector will contain electrical contacts which are internally attached to the individual insulated wires of the cable terminating in the connector. A structure may be provided at the external surface of the machine which can mate with the connector so that the machine will derive power passing through the cable.
In ordinary household caps and connectors, there are normally only two wires and such wires are those which extend for example from a wall outlet to a lamp or to a fan or other household appliance. Numerous more complex household appliances, such as vacuum cleaners and the like, have three wires, two of which carry the power and a third of which is the grounding wire of the cable. In factories, mines, and other industrial sites, the cables may have three or four wires which carry power or which carry power and ground, and in some applications, five wires are needed.
Where the form of cap or connector which is employed is of the so-called locking variety, the device has locking blades and the use of such caps and connectors involves an insertion of the blades of the cap into matching blade ports of the connector and the turning of the cap relative to the connector in order to lock the locking blades in place in the connector. As a practical matter, the number of locking blades which can be employed around the face of a cap or connector is limited to four, simply because of the size of the individual locking blades and the need for the larger blade ports in the connector into which the blades are inserted and then partially rotated in accomplishing the locking action. Because of this limitation of space in the conventional cylinderical cap and matching cylinderical connector of the locking variety, the fifth electrical blade and contact has been a central axially located blade and contact. The center contacts can be of the pin and sleeve variety in-as-much as the locking action is accomplished by the four blades located in a circular pattern between the center pin and the outer perimiter of the cap. Similarly, the center contact of the connector which receives the center pin of the cap is of the non-locking variety in-as-much as the four contacts of the connector extend in an arc in a circular formation around the center contact between the center contact in the outer perimeter of the connector.
Most of the five-wire caps and connectors of the prior art have been characterized by a means at the rear of the center pin or center sleeve of the cap or connector, respectively, which has a somewhat awkward and cumbersome means for connecting the fifth and central wire of the five-wire cable to the respective pin or sleeve of the five-wire cap or connector.
Some specific structures which have been produced and which provide five-wire termination are a connector of Pass and Seymour and this structure has a center pin which has an axial thread at its internal end and has a shallow metal cup about the threaded internal end of the pin. Electrical eonnection to a cable wire is made by threading a screw into the axial threaded opening, wrapping the wire about the screw and tightening the screw to hold the wire in place in electrical contact with the internal end of the pin or sleeve. This is an awkward way of connecting a wire to the central pin or sleeve.
Another five-wire cap has a center pin and has a metal strip extending from the portion of the center pin where it enters the face of the cap. The metal strip provides a conducting path between the center pin and an assembly for assembling portions of the cap together. The assembly screw extends through the other end of the strip. There is, in this structure, no simple means for attachment of a fifth wire on the inside portion of the cap.
A structure of Bryant Co. has a center pin which extends through an insulating housing and which terminates in a cylinderical oversize pin terminal having a screw hole recessed into one side and having a wire entry port opening from its rear surface. The oversize pin is uninsulated.
Another five-wire plug of Pass and Seymour has a center pin which terminates in a centrally threaded plate at the internal end of the pin so that a screw can be threaded axially into the threaded opening in the rear plate and so that a wire can be wound about the screw to form a loop in a plan generally parallel both to the plane of the rear surface of the cap and also to the front surface of the cap, rather than extending axially into the screw terminal as is the case with the four screw terminals which are associated with the other four blades of the cap.
One characteristic which is common to all of these prior art devices is that there is no means by which the inner end of the pin or screw terminal associated with the inner end of the pin may be itself insulated. Accordingly, the entire surface of the inner end of the pin is at the potential of the pin itself and this may be ground potential or live potential depending on the manner in which the five-wire device is connected. Also, there is relatively inferior means for attaching a wire to the wire terminal at the inner end of the pin.